beamforming - acesolution.com.tw
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LitePoint Confidential
L i t e P o i n t C o n f i d e n t i a l © 2 0 1 2 L i t e P o i n t , A T e r a d y n e C o m p a n y . A l l r i g h t s r e s e r v e d .
產品經理 黃丕先生
Beamforming創造產品差異化 如何最佳化測試
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Beamforming
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• A multi-antenna signal processing technology - Combine antenna elements to form a directional ‘beam’ - Direct the signal energy in a desired angular direction
• Two types of beamforming - Explicit – both the Beamformer and Beamformee support BF - Implicit – only the Beamformer has to support BF
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Beamforming Experiment
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• 3x3 AP as the DUT - BF on and off
• SISO client • 802.11ac 80MHz @ 5GHz • IxChariot running on external PC for throughput measurement
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Beamforming Experiment Setup DUT
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Throughput With vs. Without Beamforming
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Site Beamformed? RSSI (dBm)
Average (Mbps)
Max (Mbps)
Min (Mbps)
1 Yes -79 18.28 30.77 1.26
1 No -82 10.75 14.55 0.45
2 Yes -56 210.21 280.91 110.67
2 No -58 209.98 281.23 108.19
3 Yes -49 265.12 320.82 180.12
3 No -50 264.19 316.87 171.12
4 Yes -62 120.73 200.01 60.9
4 No -65 105.99 201.11 58.23
5 Yes -62 130.83 220.01 69.9
5 No -63 120.83 209.83 64.31
• When signal is strong (~-60dBm), IBF has little benefit • When signal is weak (~-80dBm), IBF significantly improves the throughput
>50% improvement
No significant improvement
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Better User Experience: Coverage Improvement
Normal operation mode (no BF)
BF mode
MIMO zone CDD/ BF zone
WiFi Coverage Improvement
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Implicit Beamforming: how it works
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• Beamformer (AP) does all the work! - Acquire the uplink channel information from a normal client transmission - Apply a special Beamformer matrix to convert the uplink to downlink channel - Use the downlink channel and beamform to the client direction
• Pros - Transparent to Beamformee (client), hence support legacy client devices - No signaling overhead to setup beamforming
• Cons - Not as accurate as explicit beamforming, hence the performance is limited
Start DL BF
… Repeat
Estimate UL channel
Beamformer Beamformee
Normal transmission
Convert to DL channel
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Implicit Beamforming: what need to be tested
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• Test requirements - Calibration: special routine required to calibrate phase and gain difference
for each Beamforming chain (due to PA, switch, FEM difference in each chain). This needs to be done on every DUT as Beamforming is sensitive to shift in phase and gain that varies from DUT to DUT
- Verification: compare received power difference between BF and non-BF
• Supported on the IQxel family through IQfact+
Special calibration required
3x3 chip
DUT
Rx
Rx
Rx
Tx
Tx
Tx
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Explicit Beamforming: how it works
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• Both Beamformer and Beamformee need to support beamforming - Run a training sequence before beamforming - This sequence is carried out periodically as the channel is not static
• Pros - Accurate DL channel information, hence the best BF performance
• Cons - BF have to be supported by both Beamformer and beamformee, hence not
compatible with legacy devices - BF training overhead
BF Sounding packets Channel estimation [H]DL
Return BF report
Start DL BF …
Repeat
Periodic
Beamformer Beamformee
Apply [H]DL Generate BF report
Decode BF report
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Explicit Beamforming: what need to be tested
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• Test requirements • Calibration: no special requirement • Verification: Beamformer, Beamformee or both (if supported by DUT)
need to be verified separately. The tester has the ability to emulate Beamformer and Beamformee, and can also manipulate the channel (V matrix)
• Supported on the IQxel family
NDPA NDP
SIFS
Sounding Feedback SIFS
IQxel TX
DUT TX
NDPA NDP
SIFS
Sounding Feedback SIFS SIFS
BF packet … BF packet
IQxel TX
DUT TX
Beamformee test:
Beamformer test:
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LitePoint Solution
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IQxel-M8: High Volume Connectivity Test Solution
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• High throughput enabled by advanced system architecture • Packet Engine™ optimizes testing of packet-based technologies • Build in multi-DUT test capability to minimize DUT control time • Synchronous and/or asynchronous test flows
• Comprehensive technology coverage • WiFi a/b/g/n/p/ac • BT v1 to 4.2 • 802.11ah, ZigBee, DECT
• Manufacturing simplicity • Fully calibrated, internal signal path routing – no external switches needed • Per-port level control – compensates for DUT to DUT path loss variation • Support factory efficiency features
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Flexible Figuration for SISO/MIMO/IBF Test
1 2 3 4
• 4 DUT 2x2 true MIMO/IBF
• 8 DUT SISO
1 2 3 4 5 6 7 8
• 8 DUT composite MIMO/IBF
1 2 3 4 5 6 7 8
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High Throughput through Multiple Methods
Advanced Test Methods through Standards Knowledge
Test multiple Devices in Parallel
. . .
Deep IC knowledge and partnerships drive new Test Methods
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Turn-key solution to optimize throughput, enable fast production
ramp and minimize software development effort
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Built for the Tough Factory Environment
Rugged design. Torque-tolerant N-type RF
connectors
Low power consumption and efficient cooling for operation in
hot factory environment.
Simple user interface. Minimizes operator training,
enhance reliability.
Factory efficiency features to simplify maintenance and
improve yield
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